[whatwg] style sheet blocking scripts

Jonas Sicking jonas at sicking.cc
Wed Dec 9 14:57:56 PST 2009

On Wed, Dec 9, 2009 at 2:10 PM, James Robinson <jamesr at google.com> wrote:
> 2009/12/9 tali garsiel <t_garsiel at hotmail.com>
>> Well, not completely.
>> Regarding the first question- Webkit guys told me (on their IRC channel)
>> that the don't block the parser and only block scripts that request visual
>> information, so I'm still  confused.
> Here's my understanding of the implementation inside WebKit currently:
> During parsing, WebKit does not block the parser on stylesheet loads, but
> does block external scripts from running until previously-encountered
> stylesheets have loaded.  WebKit does not suspend script execution on
> requests for visual information if stylesheets have not loaded (for example
> for inline scripts or in the case of stylesheets added dynamically after
> parsing has completed).  WebKit does suspend parsing of the document on
> script loads, but has a speculative preloader to attempt to start fetches
> for resources past the <script> tag.

Why does webkit treat external scripts different from inline scripts
here? I.e. why is an inline script allowed to run even if there are
pending stylesheet loads, but external scripts not? That seems
inconsistent and confusing.

Is this considered a bug or desired behavior?

/ Jonas

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